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            <div class="post-toc animated"><ol class="nav"><li class="nav-item nav-level-1"><a class="nav-link" href="#%E4%B8%80%E3%80%81exec%E5%87%BD%E6%95%B0%E6%97%8F"><span class="nav-text">一、exec函数族</span></a><ol class="nav-child"><li class="nav-item nav-level-2"><a class="nav-link" href="#1-%E4%B8%83%E4%B8%AA%E5%87%BD%E6%95%B0"><span class="nav-text">1. 七个函数</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#2-execl%E5%BC%80%E5%A4%B4"><span class="nav-text">2. execl开头</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#2-1-execl"><span class="nav-text">2.1 execl() </span></a><ol class="nav-child"><li class="nav-item nav-level-4"><a class="nav-link" href="#2-1-1-%E5%87%BD%E6%95%B0%E8%AF%B4%E6%98%8E"><span class="nav-text">2.1.1 函数说明</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#2-1-2-%E4%BD%BF%E7%94%A8%E5%AE%9E%E4%BE%8B"><span class="nav-text">2.1.2 使用实例</span></a></li></ol></li><li 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nav-level-1"><a class="nav-link" href="#%E4%BA%8C%E3%80%81-system"><span class="nav-text">二、 system() </span></a><ol class="nav-child"><li class="nav-item nav-level-2"><a class="nav-link" href="#1-%E5%87%BD%E6%95%B0%E8%AF%B4%E6%98%8E"><span class="nav-text">1. 函数说明</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#2-%E5%87%BD%E6%95%B0%E5%AE%9E%E7%8E%B0"><span class="nav-text">2. 函数实现</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#3-%E4%BD%BF%E7%94%A8%E5%AE%9E%E4%BE%8B"><span class="nav-text">3. 使用实例</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#4-%E8%80%97%E6%97%B6%E6%B5%8B%E8%AF%95%E5%AE%9E%E4%BE%8B"><span class="nav-text">4. 耗时测试实例</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#4-1-debug-printf-h"><span class="nav-text">4.1 debug_printf.h</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#4-2-system-called-c"><span class="nav-text">4.2 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          LV05-01-进程-03-在进程中执行程序
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<details class="folding-tag" blue><summary> 点击查看使用工具及版本 </summary>
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              <table>    <tr>        <td align="center" width=150px>Windows</td>        <td align="left">windows11</td>    </tr>    <tr>        <td align="center">Ubuntu</td>        <td align="left">Ubuntu16.04的64位版本</td>      </tr>    <tr>        <td align="center">VMware® Workstation 16 Pro</td>        <td align="left">16.2.3 build-19376536</td>      </tr>    <tr>        <td align="center">SecureCRT</td>        <td align="left">Version 8.7.2 (x64 build 2214)   -   正式版-2020年5月14日</td>      </tr>    <tr>        <td align="center">开发板</td>        <td align="left">正点原子 i.MX6ULL Linux阿尔法开发板</td>      </tr>    <tr>        <td align="center">uboot</td>        <td align="left">NXP官方提供的uboot，NXP提供的版本为uboot-imx-rel_imx_4.1.15_2.1.0_ga(使用的uboot版本为U-Boot 2016.03)</td>      </tr>    <tr>        <td align="center">linux内核</td>        <td align="left">linux-4.15(NXP官方提供)</td>      </tr>    <tr>        <td align="center">STM32开发板</td>        <td align="left">正点原子战舰V3(STM32F103ZET6)</td>      </tr></table>
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            </details>

<p>很多时候，我们希望父子进程可以执行不同的程序，下边就来看一看如何转而执行其他的程序吧。</p>
<h1 id="一、exec函数族"><a href="#一、exec函数族" class="headerlink" title="一、exec函数族"></a><font size=3>一、exec函数族</font></h1><h2 id="1-七个函数"><a href="#1-七个函数" class="headerlink" title="1. 七个函数"></a><font size=3>1. 七个函数</font></h2><p>exec 函数族共有 7 种不同形式的函数:</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">execl</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *pathname, <span class="type">const</span> <span class="type">char</span> *arg, ... <span class="comment">/* (char  *) NULL */</span>)</span>;</span><br><span class="line"><span class="type">int</span> <span class="title function_">execlp</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *file, <span class="type">const</span> <span class="type">char</span> *arg, ... <span class="comment">/* (char  *) NULL */</span>)</span>;</span><br><span class="line"><span class="type">int</span> <span class="title function_">execle</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *pathname, <span class="type">const</span> <span class="type">char</span> *arg, ... <span class="comment">/*, (char *) NULL, char *const envp[] */</span>)</span>;</span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">execv</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *pathname, <span class="type">char</span> *<span class="type">const</span> argv[])</span>;</span><br><span class="line"><span class="type">int</span> <span class="title function_">execvp</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *file, <span class="type">char</span> *<span class="type">const</span> argv[])</span>;</span><br><span class="line"><span class="type">int</span> <span class="title function_">execvpe</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *file, <span class="type">char</span> *<span class="type">const</span> argv[], <span class="type">char</span> *<span class="type">const</span> envp[])</span>;</span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">execve</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *pathname, <span class="type">char</span> *<span class="type">const</span> argv[], <span class="type">char</span> *<span class="type">const</span> envp[])</span>;</span><br></pre></td></tr></table></figure>

<p>【命名规律】 exec[l or v][p][e] </p>
<table>
    <tr><td align="center" width=150px>e</td><td align="left">参数必须带环境变量部分, 环境变量部分参数会成为执行exec函数期间的环境变量。</td></tr>
    <tr><td align="center" width=150px>l</td><td align="left">命令参数部分必须以 " , " 相隔, 最后1个命令参数必须是NULL，表示结束。</td></tr>
    <tr><td align="center" width=150px>v</td><td align="left">命令参数部分必须是1个以NULL结尾的字符串指针数组的头部指针。</td></tr>
    <tr><td align="center" width=150px>p</td><td align="left">执行文件部分可以不带路径, exec 函数会在 $PATH 中找。</td></tr>
</table>

<p>【参数分类】 exec 函数里的参数大概可以分成 3 个部分：执行文件部分、命令参数部分和环境变量部分。</p>
<h2 id="2-execl开头"><a href="#2-execl开头" class="headerlink" title="2. execl开头"></a><font size=3>2. execl开头</font></h2><h3 id="2-1-execl"><a href="#2-1-execl" class="headerlink" title="2.1 execl() "></a><font size=3>2.1 execl() </font></h3><h4 id="2-1-1-函数说明"><a href="#2-1-1-函数说明" class="headerlink" title="2.1.1 函数说明"></a><font size=3>2.1.1 函数说明</font></h4><p>在 linux 下可以使用 man 3 execl 命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="keyword">extern</span> <span class="type">char</span> **environ; <span class="comment">/* 手册上有写，但是似乎不写也没什么 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">execl</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *pathname, <span class="type">const</span> <span class="type">char</span> *arg, ... <span class="comment">/* (char  *) NULL */</span>)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数将新程序加载到某一进程的内存空间，将一个外部的可执行文件加载到进程的内存空间运行，使用新的程序替换旧的程序，而进程的栈、数据、以及堆数据会被新程序的相应部件所替换，然后从新程序的 main() 函数开始执行。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>pathname ： const char * 类型，参数 pathname 指向需要载入当前进程空间的新程序的路径名，既可以是绝对路径、也可以是相对路径。</li>
<li>arg ： const char * 类型，传递给执行的程序的参数列表，使用可变参数形式传递，本质上是多个字符串，以 NULL 结尾。</li>
</ul>
<p><strong>【返回值】</strong>返回值为 int 类型，调用成功将不会返回；失败将返回 -1 ，并设置 errno 。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line">execl(<span class="string">&quot;./newTest&quot;</span>, <span class="string">&quot;./newTest&quot;</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;World&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;!&quot;</span>);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong> none </p>
<h4 id="2-1-2-使用实例"><a href="#2-1-2-使用实例" class="headerlink" title="2.1.2 使用实例"></a><font size=3>2.1.2 使用实例</font></h4><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="keyword">if</span>(execl(<span class="string">&quot;/bin/ls&quot;</span>, <span class="string">&quot;ls&quot;</span>, <span class="string">&quot;-a&quot;</span>, <span class="string">&quot;-l&quot;</span>, <span class="string">&quot;./&quot;</span>, <span class="literal">NULL</span>) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;execl&quot;</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out</span><br><span class="line">./a.out # 执行程序</span><br></pre></td></tr></table></figure><p>程序执行后，终端将会显示以下信息：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">总用量 198</span><br><span class="line">drwxrwxrwx 1 root root  4096  5月 23 11:49 .</span><br><span class="line">dr-xr-xr-x 1 root root  4192  5月 23 11:49 ..</span><br><span class="line">drwxrwxrwx 1 root root  4096  3月  1 20:41 1Pictures</span><br><span class="line"><span class="meta prompt_"># </span><span class="language-bash">剩下的省略 ...</span></span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="2-2-execlp"><a href="#2-2-execlp" class="headerlink" title="2.2 execlp() "></a><font size=3>2.2 execlp() </font></h3><h4 id="2-2-1-函数说明"><a href="#2-2-1-函数说明" class="headerlink" title="2.2.1 函数说明"></a><font size=3>2.2.1 函数说明</font></h4><p>在 linux 下可以使用 man 3 execlp 命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="keyword">extern</span> <span class="type">char</span> **environ; <span class="comment">/* 手册上有写，但是似乎不写也没什么 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">execlp</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *file, <span class="type">const</span> <span class="type">char</span> *arg, ... <span class="comment">/* (char  *) NULL */</span>)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数借助 PATH 环境变量将新程序加载到某一进程的内存空间，然后从新程序的 main() 函数开始执行，与 execl 函数功能一样，只是该函数不需要给出新程序的路径。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>file ： const char * 类型，参数 file 指向需要载入当前进程空间的新程序的名称，不需要给出路径，但是要保证新程序路径存在于环境变量 PATH 中。</li>
<li>arg ： const char * 类型，传递给执行的程序的参数列表，本质上是多个字符串，以 NULL 结尾。</li>
</ul>
<p><strong>【返回值】</strong>返回值为 int 类型，调用成功将不会返回；失败将返回 -1 ，并设置 errno 。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line">execlp(<span class="string">&quot;newTest&quot;</span>, <span class="string">&quot;newTest&quot;</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;World&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;!&quot;</span>); <span class="comment">/* newTest 路径需要存在于 $PATH 中 */</span></span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong>相对于 execl ， execlp 仅要求提供新程序的名称即可，但是需要保证新程序路径存在于环境变量 $PATH 中。</p>
<h4 id="2-2-2-使用实例"><a href="#2-2-2-使用实例" class="headerlink" title="2.2.2 使用实例"></a><font size=3>2.2.2 使用实例</font></h4><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="keyword">if</span>(execlp(<span class="string">&quot;ls&quot;</span>, <span class="string">&quot;ls&quot;</span>, <span class="string">&quot;-a&quot;</span>, <span class="string">&quot;-l&quot;</span>, <span class="string">&quot;./&quot;</span>, <span class="literal">NULL</span>) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;execlp&quot;</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out</span><br><span class="line">./a.out # 执行程序</span><br></pre></td></tr></table></figure><p>程序执行后，终端将会显示以下信息：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">总用量 198</span><br><span class="line">drwxrwxrwx 1 root root  4096  5月 23 13:17 .</span><br><span class="line">dr-xr-xr-x 1 root root  4192  5月 23  2022 ..</span><br><span class="line">drwxrwxrwx 1 root root  4096  3月  1 20:41 1Pictures</span><br><span class="line"><span class="meta prompt_"># </span><span class="language-bash">剩下的省略 ...</span></span><br></pre></td></tr></table></figure>
              </div>
            </details>



<h3 id="2-3-execle"><a href="#2-3-execle" class="headerlink" title="2.3 execle() "></a><font size=3>2.3 execle() </font></h3><h4 id="2-3-1-函数说明"><a href="#2-3-1-函数说明" class="headerlink" title="2.3.1 函数说明"></a><font size=3>2.3.1 函数说明</font></h4><p>在 linux 下可以使用 man 3 execle 命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">execle</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *pathname, <span class="type">const</span> <span class="type">char</span> *arg, ... <span class="comment">/*, (char *) NULL, char *const envp[] */</span>)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数将新程序加载到某一进程的内存空间，将一个外部的可执行文件加载到进程的内存空间运行，使用新的程序替换旧的程序，而进程的栈、数据、以及堆数据会被新程序的相应部件所替换，然后从新程序的 main() 函数开始执行。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>pathname ： const char * 类型，参数 pathname 指向需要载入当前进程空间的新程序的路径名，既可以是绝对路径、也可以是相对路径。</li>
<li>arg ： const char * 类型，传递给执行的程序的参数列表，本质上是多个字符串，以 NULL 结尾。</li>
<li>envp[] ： char *const 类型数组，即是一个字符串指针数组，指定了新程序的环境变量列表，参数 envp 其实对应于新程序的 environ 数组，同样也是以 NULL 结束，所指向的字符串格式为 name&#x3D;value 。</li>
</ul>
<p><strong>【返回值】</strong>返回值为 int 类型，调用成功将不会返回；失败将返回 -1 ，并设置 errno 。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="type">char</span> *env_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;NAME=app&quot;</span>, <span class="string">&quot;AGE=25&quot;</span>, <span class="string">&quot;SEX=man&quot;</span>, <span class="literal">NULL</span>&#125;;</span><br><span class="line">execle(<span class="string">&quot;./newTest&quot;</span>, <span class="string">&quot;./newTest&quot;</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;fanhua&quot;</span>, <span class="literal">NULL</span>, env_arr);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong></p>
<p>（1）对 execle() 的成功调用将永不返回，而且也无需检查它的返回值，一旦该函数返回，就表明它发生了错误。</p>
<p>（2）当使用 execle() 传入命令行及环境变量参数时，都是遇到 NULL 就结束，新执行程序的命令行参数的 argv[0] 由调用该新程序的程序传入的第一个参数决定。</p>
<h4 id="2-3-2-使用实例"><a href="#2-3-2-使用实例" class="headerlink" title="2.3.2 使用实例"></a><font size=3>2.3.2 使用实例</font></h4><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <div class="tabs" id="tabname1"><ul class="nav-tabs"><li class="tab active"><a href="#tabname1-1">test.c</a></li><li class="tab"><a href="#tabname1-2">newTest.c</a></li></ul><div class="tab-content"><div class="tab-pane active" id="tabname1-1"><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">int</span> ret = <span class="number">0</span>;</span><br><span class="line">	<span class="type">char</span> *env_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;NAME=app&quot;</span>, <span class="string">&quot;AGE=25&quot;</span>, <span class="string">&quot;SEX=man&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;Fanhua=1&quot;</span>&#125;;</span><br><span class="line">	</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;This is test.c!\n&quot;</span>);</span><br><span class="line">	ret = execle(<span class="string">&quot;./newTest&quot;</span>, <span class="string">&quot;./newTest&quot;</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;fanhua&quot;</span>, <span class="literal">NULL</span>, env_arr);</span><br><span class="line">	<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;execle error&quot;</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令生成可执行文件：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out</span><br></pre></td></tr></table></figure></div><div class="tab-pane" id="tabname1-2"><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">extern</span> <span class="type">char</span> **environ;</span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">char</span> **ep = <span class="literal">NULL</span>;</span><br><span class="line">	<span class="type">int</span> i = <span class="number">0</span>;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;This is new application!argc = %d\n&quot;</span>, argc);</span><br><span class="line">	<span class="keyword">for</span> (i = <span class="number">0</span>; i &lt; argc; i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;argv[%d]: %s\n&quot;</span>, i, argv[i]);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="built_in">puts</span>(<span class="string">&quot;env:&quot;</span>);</span><br><span class="line">	<span class="keyword">for</span> (ep = environ; *ep != <span class="literal">NULL</span>; ep++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot; %s\n&quot;</span>, *ep);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令生成可执行文件：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">gcc newTest.c -o newTest -Wall # 生成可执行文件 newTest</span><br></pre></td></tr></table></figure></div></div></div><p>在终端执行以下命令运行 a.out ：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./a.out # 执行程序</span><br></pre></td></tr></table></figure><p>程序执行后，终端将会显示以下信息：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">This is test.c!</span><br><span class="line">This is new application!argc = 3</span><br><span class="line">argv[0]: ./newTest</span><br><span class="line">argv[1]: Hello</span><br><span class="line">argv[2]: fanhua</span><br><span class="line">env:</span><br><span class="line"> NAME=app</span><br><span class="line"> AGE=25</span><br><span class="line"> SEX=man</span><br></pre></td></tr></table></figure><p>可以发现， NULL 后边的参数都没有打印出来，且新执行程序的 argv[0] 不再是程序名称，而是与传入的参数保持一致。</p>
              </div>
            </details>

<h2 id="3-execv开头"><a href="#3-execv开头" class="headerlink" title="3. execv开头"></a><font size=3>3. execv开头</font></h2><h3 id="3-1-execv"><a href="#3-1-execv" class="headerlink" title="3.1 execv() "></a><font size=3>3.1 execv() </font></h3><h4 id="3-1-1-函数说明"><a href="#3-1-1-函数说明" class="headerlink" title="3.1.1 函数说明"></a><font size=3>3.1.1 函数说明</font></h4><p>在 linux 下可以使用 man 3 execv 命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="keyword">extern</span> <span class="type">char</span> **environ; <span class="comment">/* 手册上有写，但是似乎不写也没什么 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">execv</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *pathname, <span class="type">char</span> *<span class="type">const</span> argv[])</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数将新程序加载到某一进程的内存空间，将一个外部的可执行文件加载到进程的内存空间运行，使用新的程序替换旧的程序，而进程的栈、数据、以及堆数据会被新程序的相应部件所替换，然后从新程序的 main() 函数开始执行。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>pathname ： const char * 类型，参数 pathname 指向需要载入当前进程空间的新程序的路径名，既可以是绝对路径、也可以是相对路径。</li>
<li>argv[] ： char *const 类型的数组，指定了传递给新程序的命令行参数。该参数是一个字符串数组，该数组对应于 main(int argc, char *argv[]) 函数的第二个参数 argv ，且格式也与之相同，是由字符串指针所组成的数组，以 NULL 结束。 argv[0] 对应的便是新程序自身路径名。</li>
</ul>
<p><strong>【返回值】</strong>返回值为 int 类型，调用成功将不会返回；失败将返回 -1 ，并设置 errno 。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="type">char</span>  *arg[] = &#123;<span class="string">&quot;./newTest&quot;</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;World&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;!&quot;</span>&#125;;</span><br><span class="line">execv(<span class="string">&quot;./newTest&quot;</span>, arg);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong> none </p>
<h4 id="3-1-2-使用实例"><a href="#3-1-2-使用实例" class="headerlink" title="3.1.2 使用实例"></a><font size=3>3.1.2 使用实例</font></h4><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">char</span>  *arg[] = &#123;<span class="string">&quot;ls&quot;</span>, <span class="string">&quot;-a&quot;</span>, <span class="string">&quot;-l&quot;</span>, <span class="string">&quot;./&quot;</span>, <span class="literal">NULL</span>&#125;;</span><br><span class="line">	<span class="keyword">if</span>(execv(<span class="string">&quot;/bin/ls&quot;</span>, arg) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;execv&quot;</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out</span><br><span class="line">./a.out # 执行程序</span><br></pre></td></tr></table></figure><p>程序执行后，终端将会显示以下信息：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">总用量 198</span><br><span class="line">drwxrwxrwx 1 root root  4096  5月 23 13:47 .</span><br><span class="line">dr-xr-xr-x 1 root root  4192  5月 23  2022 ..</span><br><span class="line">drwxrwxrwx 1 root root  4096  3月  1 20:41 1Pictures</span><br><span class="line"><span class="meta prompt_"># </span><span class="language-bash">剩下的省略 ...</span></span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="3-2-execvp"><a href="#3-2-execvp" class="headerlink" title="3.2 execvp() "></a><font size=3>3.2 execvp() </font></h3><h4 id="3-2-1-函数说明"><a href="#3-2-1-函数说明" class="headerlink" title="3.2.1 函数说明"></a><font size=3>3.2.1 函数说明</font></h4><p>在 linux 下可以使用 man 3 execvp 命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="keyword">extern</span> <span class="type">char</span> **environ; <span class="comment">/* 手册上有写，但是似乎不写也没什么 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">execvp</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *file, <span class="type">char</span> *<span class="type">const</span> argv[])</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数借助 PATH 环境变量将新程序加载到某一进程的内存空间，然后从新程序的 main() 函数开始执行，与 execv 函数功能一样，只是该函数不需要给出新程序的路径。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>file ： const char * 类型，参数 file 指向需要载入当前进程空间的新程序的名称，不需要给出路径，但是要保证新程序路径存在于环境变量 PATH 中。</li>
<li>argv[] ： char *const 类型的数组，指定了传递给新程序的命令行参数。该参数是一个字符串数组，该数组对应于 main(int argc, char *argv[]) 函数的第二个参数 argv ，且格式也与之相同，是由字符串指针所组成的数组，以 NULL 结束。 argv[0] 对应的便是新程序自身路径名。</li>
</ul>
<p><strong>【返回值】</strong>返回值为 int 类型，调用成功将不会返回；失败将返回 -1 ，并设置 errno 。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="type">char</span>  *arg[] = &#123;<span class="string">&quot;newTest&quot;</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;World&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;!&quot;</span>&#125;;</span><br><span class="line">execvp(<span class="string">&quot;newTest&quot;</span>, arg);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong>相对于 execv ， execvp 仅要求提供新程序的名称即可。</p>
<h4 id="3-2-2-使用实例"><a href="#3-2-2-使用实例" class="headerlink" title="3.2.2 使用实例"></a><font size=3>3.2.2 使用实例</font></h4><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="keyword">if</span>(execvp(<span class="string">&quot;ls&quot;</span>, <span class="string">&quot;ls&quot;</span>, <span class="string">&quot;-a&quot;</span>, <span class="string">&quot;-l&quot;</span>, <span class="string">&quot;./&quot;</span>, <span class="literal">NULL</span>) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;execvp&quot;</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out</span><br><span class="line">./a.out # 执行程序</span><br></pre></td></tr></table></figure><p>程序执行后，终端将会显示以下信息：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">总用量 198</span><br><span class="line">drwxrwxrwx 1 root root  4096  5月 23 13:17 .</span><br><span class="line">dr-xr-xr-x 1 root root  4192  5月 23  2022 ..</span><br><span class="line">drwxrwxrwx 1 root root  4096  3月  1 20:41 1Pictures</span><br><span class="line"><span class="meta prompt_"># </span><span class="language-bash">剩下的省略</span></span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="3-3-execvpe"><a href="#3-3-execvpe" class="headerlink" title="3.3 execvpe() "></a><font size=3>3.3 execvpe() </font></h3><h4 id="3-3-1-函数说明"><a href="#3-3-1-函数说明" class="headerlink" title="3.3.1 函数说明"></a><font size=3>3.3.1 函数说明</font></h4><p>在 linux 下可以使用 man 3 execvpe 命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="keyword">extern</span> <span class="type">char</span> **environ; <span class="comment">/* 手册上有写，但是似乎不写也没什么 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">execvpe</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *file, <span class="type">char</span> *<span class="type">const</span> argv[], <span class="type">char</span> *<span class="type">const</span> envp[])</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数将新程序加载到某一进程的内存空间，将一个外部的可执行文件加载到进程的内存空间运行，使用新的程序替换旧的程序，而进程的栈、数据、以及堆数据会被新程序的相应部件所替换，然后从新程序的 main() 函数开始执行。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>file ： const char * 类型，参数 file 指向需要载入当前进程空间的新程序的名称，不需要给出路径，但是要保证新程序路径存在于环境变量 PATH 中。</li>
<li>argv[] ： char *const 类型的数组，指定了传递给新程序的命令行参数。该参数是一个字符串数组，该数组对应于 main(int argc, char *argv[]) 函数的第二个参数 argv ，且格式也与之相同，是由字符串指针所组成的数组，以 NULL 结束。 argv[0] 对应的便是新程序自身路径名。</li>
<li>envp[] ： char *const 类型数组，即是一个字符串指针数组，指定了新程序的环境变量列表，参数 envp 其实对应于新程序的 environ 数组，同样也是以 NULL 结束，所指向的字符串格式为 name&#x3D;value 。</li>
</ul>
<p><strong>【返回值】</strong>返回值为 int 类型，调用成功将不会返回；失败将返回 -1 ，并设置 errno 。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="type">char</span> *arg_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;newTest&quot;</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;World&quot;</span>, <span class="literal">NULL</span>, &#125;; </span><br><span class="line"><span class="type">char</span> *env_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;NAME=app&quot;</span>, <span class="string">&quot;AGE=25&quot;</span>, <span class="string">&quot;SEX=man&quot;</span>, <span class="literal">NULL</span>&#125;;</span><br><span class="line">execle(<span class="string">&quot;newTest&quot;</span>, arg_arr, <span class="literal">NULL</span>, env_arr);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong></p>
<p>（1）对 execvpe() 的成功调用将永不返回，而且也无需检查它的返回值，一旦该函数返回，就表明它发生了错误。</p>
<p>（2）当使用 execvpe() 传入命令行及环境变量参数时，都是遇到 NULL 就结束，新执行程序的命令行参数的 argv[0] 由调用该新程序的程序传入的第一个参数决定。</p>
<h4 id="3-3-2-使用实例"><a href="#3-3-2-使用实例" class="headerlink" title="3.3.2 使用实例"></a><font size=3>3.3.2 使用实例</font></h4><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <p>首先添加环境变量（不添加的话，可能会报文件找不到。）：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta prompt_"># </span><span class="language-bash">临时改变当前终端的环境变量</span></span><br><span class="line">export PATH=/home/hk/2Sharedfiles:$PATH</span><br><span class="line"><span class="meta prompt_"># </span><span class="language-bash">查看环境变量是否添加成功</span></span><br><span class="line">echo $PATH</span><br></pre></td></tr></table></figure><div class="tabs" id="tabname2"><ul class="nav-tabs"><li class="tab active"><a href="#tabname2-1">test.c</a></li><li class="tab"><a href="#tabname2-2">newTest.c</a></li></ul><div class="tab-content"><div class="tab-pane active" id="tabname2-1"><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">int</span> ret = <span class="number">0</span>;</span><br><span class="line">    <span class="type">char</span> *arg_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;newTest&quot;</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;qidaink&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;!&quot;</span>&#125;;</span><br><span class="line">	<span class="type">char</span> *env_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;NAME=app&quot;</span>, <span class="string">&quot;AGE=25&quot;</span>, <span class="string">&quot;SEX=man&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;Fanhua=1&quot;</span>&#125;;</span><br><span class="line">	</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;This is test.c!\n&quot;</span>);</span><br><span class="line">	ret = execvpe(<span class="string">&quot;newTest&quot;</span>, arg_arr, env_arr);</span><br><span class="line">	<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;execvpe error&quot;</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令生成可执行文件：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out</span><br></pre></td></tr></table></figure><p>不过很奇怪的就是，它报了下边的警告：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">test.c: In function ‘main’:</span><br><span class="line">test.c:11:8: warning: implicit declaration of function ‘execvpe’; did you mean ‘execvp’? [-Wimplicit-function-declaration]</span><br><span class="line">   11 |  ret = execvpe(&quot;newTest&quot;, arg_arr, env_arr);</span><br><span class="line">      |        ^~~~~~~</span><br><span class="line">      |        execvp</span><br><span class="line"></span><br></pre></td></tr></table></figure><p>我查了手册，这个函数是存在的，所以目前还未知原因。后边再补充吧。</p></div><div class="tab-pane" id="tabname2-2"><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">extern</span> <span class="type">char</span> **environ;</span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">char</span> **ep = <span class="literal">NULL</span>;</span><br><span class="line">	<span class="type">int</span> i = <span class="number">0</span>;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;This is new application!argc = %d\n&quot;</span>, argc);</span><br><span class="line">	<span class="keyword">for</span> (i = <span class="number">0</span>; i &lt; argc; i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;argv[%d]: %s\n&quot;</span>, i, argv[i]);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="built_in">puts</span>(<span class="string">&quot;env:&quot;</span>);</span><br><span class="line">	<span class="keyword">for</span> (ep = environ; *ep != <span class="literal">NULL</span>; ep++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot; %s\n&quot;</span>, *ep);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令生成可执行文件：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">gcc newTest.c -o newTest -Wall # 生成可执行文件 newTest</span><br></pre></td></tr></table></figure></div></div></div><p>在终端执行以下命令运行 a.out ：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./a.out # 执行程序</span><br></pre></td></tr></table></figure><p>程序执行后，终端将会显示以下信息：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">This is test.c!</span><br><span class="line">This is new application!argc = 3</span><br><span class="line">argv[0]: newTest</span><br><span class="line">argv[1]: Hello</span><br><span class="line">argv[2]: qidaink</span><br><span class="line">env:</span><br><span class="line"> NAME=app</span><br><span class="line"> AGE=25</span><br><span class="line"> SEX=man</span><br></pre></td></tr></table></figure><p>可以发现， NULL 后边的参数都没有打印出来，且新执行程序的 argv[0] 不再是程序名称，而是与传入的参数保持一致。</p>
              </div>
            </details>



<h3 id="3-4-execve"><a href="#3-4-execve" class="headerlink" title="3.4 execve() "></a><font size=3>3.4 execve() </font></h3><h4 id="3-4-1-函数说明"><a href="#3-4-1-函数说明" class="headerlink" title="3.4.1 函数说明"></a><font size=3>3.4.1 函数说明</font></h4><p>在 linux 下可以使用 man 3 execve 命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">execve</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *pathname, <span class="type">char</span> *<span class="type">const</span> argv[], <span class="type">char</span> *<span class="type">const</span> envp[])</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数将新程序加载到某一进程的内存空间，将一个外部的可执行文件加载到进程的内存空间运行，使用新的程序替换旧的程序，而进程的栈、数据、以及堆数据会被新程序的相应部件所替换，然后从新程序的 main() 函数开始执行。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li>pathname ： const char * 类型，参数 pathname 指向需要载入当前进程空间的新程序的路径名，既可以是绝对路径、也可以是相对路径。</li>
<li>argv[] ： char *const 类型的数组，指定了传递给新程序的命令行参数。该参数是一个字符串数组，该数组对应于 main(int argc, char *argv[]) 函数的第二个参数 argv ，且格式也与之相同，是由字符串指针所组成的数组，以 NULL 结束。 argv[0] 对应的便是新程序自身路径名。</li>
<li>envp[] ： char *const 类型数组，即是一个字符串指针数组，指定了新程序的环境变量列表，参数 envp 其实对应于新程序的 environ 数组，同样也是以 NULL 结束，所指向的字符串格式为 name&#x3D;value 。</li>
</ul>
<p><strong>【返回值】</strong>返回值为 int 类型，调用成功将不会返回；失败将返回 -1 ，并设置 errno 。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="type">char</span> *arg_arr[<span class="number">5</span>] = &#123;<span class="literal">NULL</span>, <span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;World&quot;</span>, <span class="literal">NULL</span>&#125;; </span><br><span class="line"><span class="type">char</span> *env_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;NAME=app&quot;</span>, <span class="string">&quot;AGE=25&quot;</span>, <span class="string">&quot;SEX=man&quot;</span>, <span class="literal">NULL</span>&#125;;</span><br><span class="line">execve(argv[<span class="number">1</span>], arg_arr, env_arr);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong></p>
<p>（1）对 execve() 的成功调用将永不返回，而且也无需检查它的返回值，一旦该函数返回，就表明它发生了错误。</p>
<p>（2）当使用 execve() 传入命令行及环境变量参数时，都是遇到 NULL 就结束，新执行程序的命令行参数的 argv[0] 由调用该新程序的程序传入的第一个参数决定。</p>
<h4 id="3-4-2-使用实例"><a href="#3-4-2-使用实例" class="headerlink" title="3.4.2 使用实例"></a><font size=3>3.4.2 使用实例</font></h4><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <div class="tabs" id="tabname3"><ul class="nav-tabs"><li class="tab active"><a href="#tabname3-1">test.c</a></li><li class="tab"><a href="#tabname3-2">newTest.c</a></li></ul><div class="tab-content"><div class="tab-pane active" id="tabname3-1"><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">int</span> ret = <span class="number">0</span>;</span><br><span class="line">	<span class="type">char</span> *arg_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;Hello&quot;</span>, <span class="string">&quot;world&quot;</span>, <span class="string">&quot;!&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;Fanhua&quot;</span>&#125;;</span><br><span class="line">	<span class="type">char</span> *env_arr[<span class="number">5</span>] = &#123;<span class="string">&quot;NAME=app&quot;</span>, <span class="string">&quot;AGE=25&quot;</span>, <span class="string">&quot;SEX=man&quot;</span>, <span class="literal">NULL</span>, <span class="string">&quot;Fanhua=1&quot;</span>&#125;;</span><br><span class="line">	</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;This is test.c!\n&quot;</span>);</span><br><span class="line">	ret = execve(<span class="string">&quot;./newTest&quot;</span>, arg_arr, env_arr);</span><br><span class="line">	<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;execve error&quot;</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令生成可执行文件：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out</span><br></pre></td></tr></table></figure></div><div class="tab-pane" id="tabname3-2"><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">extern</span> <span class="type">char</span> **environ;</span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">char</span> **ep = <span class="literal">NULL</span>;</span><br><span class="line">	<span class="type">int</span> i = <span class="number">0</span>;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;This is new application!argc = %d\n&quot;</span>, argc);</span><br><span class="line">	<span class="keyword">for</span> (i = <span class="number">0</span>; i &lt; argc; i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;argv[%d]: %s\n&quot;</span>, i, argv[i]);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="built_in">puts</span>(<span class="string">&quot;env:&quot;</span>);</span><br><span class="line">	<span class="keyword">for</span> (ep = environ; *ep != <span class="literal">NULL</span>; ep++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot; %s\n&quot;</span>, *ep);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令生成可执行文件：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">gcc newTest.c -o newTest -Wall # 生成可执行文件 newTest</span><br></pre></td></tr></table></figure></div></div></div><p>在终端执行以下命令运行 a.out ：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./a.out # 执行程序</span><br></pre></td></tr></table></figure><p>程序执行后，终端将会显示以下信息：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">This is test.c!</span><br><span class="line">This is new application!argc = 3</span><br><span class="line">argv[0]: Hello</span><br><span class="line">argv[1]: world</span><br><span class="line">argv[2]: !</span><br><span class="line">env:</span><br><span class="line"> NAME=app</span><br><span class="line"> AGE=25</span><br><span class="line"> SEX=man</span><br></pre></td></tr></table></figure><p>可以发现， NULL 后边的参数都没有打印出来，且新执行程序的 argv[0] 不再是程序名称，而是与传入的参数保持一致。</p>
              </div>
            </details>

<h1 id="二、-system"><a href="#二、-system" class="headerlink" title="二、 system() "></a><font size=3>二、 system() </font></h1><h2 id="1-函数说明"><a href="#1-函数说明" class="headerlink" title="1. 函数说明"></a><font size=3>1. 函数说明</font></h2><p>在 linux 下可以使用 man 3 system 命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">system</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *command)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数可以在我们当前程序当中执行任意 shell 命令。</p>
<details class="folding-tag" blue><summary> 点击查看函数详细说明 </summary>
              <div class='content'>
              <p>system() 函数其内部的是通过调用 fork() 、 execl() 以及 waitpid() 这三个函数来实现它的功能。 system() 会调用 fork() 创建一个子进程来运行 shell （可以把这个子进程称为 shell 进程），并通过 shell 执行参数 command 所指定的命令。</p>
              </div>
            </details>

<p><strong>【函数参数】</strong></p>
<ul>
<li>command ： const char * 类型，参数 command 指向需要执行的 shell 命令，以字符串的形式提供，如 “ls -al” 等。</li>
</ul>
<p><strong>【返回值】</strong>返回值为 int 类型，当参数 command 为 NULL ，如果 shell 可用则返回一个非 0 值，若不可用则返回 0 ；针对一些非 UNIX 系统，该系统上可能是没有 shell 的，这样就会导致 shell 不可能；如果 command 参数不为 NULL ，则返回值从以下的各种情况所决定：</p>
<p>（1）如果无法创建子进程或无法获取子进程的终止状态，那么 system() 返回-1；</p>
<p>（2）如果子进程不能执行 shell ，则 system() 的返回值就好像是子进程通过调用 _exit(127) 终止了；</p>
<p>（3）如果所有的系统调用都成功， system() 函数会返回执行 command 的 shell 进程的终止状态。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line">system(<span class="string">&quot;ps -l&quot;</span>);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong>system() 的主要优点在于使用上方便简单，编程时无需自己处理对 fork() 、 exec 函数、 waitpid() 以及 exit() 等调用细节， system() 内部会代为处理；当然这些优点通常是以牺牲效率为代价的，使用 system() 运行 shell 命令需要至少创建两个进程，一个进程用于运行 shell 、另外一个或多个进程则用于运行参数 command 中解析出来的命令，每一个命令都会调用一次 exec 函数来执行；所以从这里可以看出，使用 system() 函数其效率会降低，如果我们的程序对效率或速度有所要求，那么建议不要直接使用 system() 。</p>
<h2 id="2-函数实现"><a href="#2-函数实现" class="headerlink" title="2. 函数实现"></a><font size=3>2. 函数实现</font></h2><p>上边的了解仅仅够我们了解到如何使用这个函数，以及这个函数有什么功能，那他内部是怎样的，使用过程中会有什么影响？我们先来看一下这个函数的源码，很遗憾，我没找到，它在 stdlib.h 文件中声明，但是我还是没有找到源码，就网上搜了一个，应该大差不差：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">system</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *cmdstring)</span></span><br><span class="line"></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">pid_t</span> pid;</span><br><span class="line">	<span class="type">int</span> status;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">if</span> (cmdstring == <span class="literal">NULL</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">return</span> (<span class="number">1</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">if</span> ((pid = fork()) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		status = <span class="number">-1</span>;</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">else</span> <span class="keyword">if</span> (pid == <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line"></span><br><span class="line">		execl(<span class="string">&quot;/bin/sh&quot;</span>, <span class="string">&quot;sh&quot;</span>, <span class="string">&quot;-c&quot;</span>, cmdstring, (<span class="type">char</span> *)<span class="number">0</span>);</span><br><span class="line">		-<span class="built_in">exit</span>(<span class="number">127</span>); <span class="comment">// 子进程正常执行则不会执行此语句</span></span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">else</span></span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">while</span> (waitpid(pid, &amp;status, <span class="number">0</span>) &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			<span class="keyword">if</span> (errno != EINTER)</span><br><span class="line">			&#123;</span><br><span class="line">				status = <span class="number">-1</span>;</span><br><span class="line">				<span class="keyword">break</span>;</span><br><span class="line">			&#125;</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> status;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p>从这里可以看出其实system函数调用之后会创建一个子进程，子进程调用execl()去执行相应的shell命令，然后父进程会调用waitpid等待子进程退出，对子进城进程回收，这也就意味着，调用system的进程在这个时候会被阻塞，当执行的shell命令需要较长时间才能执行完毕的时候，调用system的进程就会等待很久的时间。</p>
<h2 id="3-使用实例"><a href="#3-使用实例" class="headerlink" title="3. 使用实例"></a><font size=3>3. 使用实例</font></h2><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	system(<span class="string">&quot;ps -l&quot;</span>);</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out</span><br><span class="line">./a.out # 执行程序</span><br></pre></td></tr></table></figure><p>程序执行后，终端将会显示以下信息：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">F S   UID     PID    PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD</span><br><span class="line">0 S  1000   11992    9420  0  80   0 -  5035 do_wai pts/1    00:00:00 bash</span><br><span class="line">0 S  1000   17347   11992  0  80   0 -   595 do_wai pts/1    00:00:00 a.out</span><br><span class="line">0 S  1000   17348   17347  0  80   0 -   658 do_wai pts/1    00:00:00 sh</span><br><span class="line">0 R  1000   17350   17348  0  80   0 -  5254 -      pts/1    00:00:00 ps</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h2 id="4-耗时测试实例"><a href="#4-耗时测试实例" class="headerlink" title="4. 耗时测试实例"></a><font size=3>4. 耗时测试实例</font></h2><p>这部分会用到后边线程的一些知识，耗时的测试是通过线程来完成。</p>
<h3 id="4-1-debug-printf-h"><a href="#4-1-debug-printf-h" class="headerlink" title="4.1 debug_printf.h"></a><font size=3>4.1 debug_printf.h</font></h3><details class="folding-tag" blue><summary> 点击查看详情 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">ifndef</span> __DEBUG_PRINTF_H__</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> __DEBUG_PRINTF_H__</span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> DEBUG_ENABLE  1           <span class="comment">/* 是否开启调试信息 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> LOG_LEVEL     DEBUG_ALL   <span class="comment">/* 调试信息显示级别 */</span></span></span><br><span class="line"> </span><br><span class="line"><span class="meta">#<span class="keyword">define</span> ERROR   <span class="string">&quot;ERROR&quot;</span>           <span class="comment">/* 错误 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> WARN    <span class="string">&quot;WARN &quot;</span>           <span class="comment">/* 警告 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> INFO    <span class="string">&quot;INFO &quot;</span>           <span class="comment">/* 信息 */</span></span></span><br><span class="line"><span class="comment">/* 颜色定义——字体颜色 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> CLS_ALL        <span class="string">&quot;\033[0m&quot;</span>  <span class="comment">/* 清除所有颜色 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> F_BLACK        <span class="string">&quot;\033[30m&quot;</span> <span class="comment">/* 黑色字体 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> F_RED          <span class="string">&quot;\033[31m&quot;</span> <span class="comment">/* 红色字体 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> F_GREEN        <span class="string">&quot;\033[32m&quot;</span> <span class="comment">/* 绿色字体 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> F_YELLOW       <span class="string">&quot;\033[33m&quot;</span> <span class="comment">/* 黄色字体 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> F_BLUE         <span class="string">&quot;\033[34m&quot;</span> <span class="comment">/* 蓝色字体 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> F_PURPLE       <span class="string">&quot;\033[35m&quot;</span> <span class="comment">/* 紫色字体 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> F_CYAN         <span class="string">&quot;\033[36m&quot;</span> <span class="comment">/* 青色字体 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> F_WHITE        <span class="string">&quot;\033[37m&quot;</span> <span class="comment">/* 白色字体 */</span></span></span><br><span class="line"><span class="comment">/* 颜色定义——背景颜色 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> B_BLACK        <span class="string">&quot;\033[40m&quot;</span> <span class="comment">/* 黑色背景 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> B_RED          <span class="string">&quot;\033[41m&quot;</span> <span class="comment">/* 红色背景 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> B_GREEN        <span class="string">&quot;\033[42m&quot;</span> <span class="comment">/* 绿色背景 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> B_YELLOW       <span class="string">&quot;\033[43m&quot;</span> <span class="comment">/* 黄色背景 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> B_BLUE         <span class="string">&quot;\033[44m&quot;</span> <span class="comment">/* 蓝色背景 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> B_PURPLE       <span class="string">&quot;\033[45m&quot;</span> <span class="comment">/* 紫色背景 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> B_CYAN         <span class="string">&quot;\033[46m&quot;</span> <span class="comment">/* 青色背景 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> B_WHITE        <span class="string">&quot;\033[47m&quot;</span> <span class="comment">/* 白色背景 */</span></span></span><br><span class="line"><span class="comment">/* 颜色定义——背景的字体 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> BLACK_RED      <span class="string">&quot;\033[30;41m&quot;</span> <span class="comment">/* 红底黑字 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> BLACK_GREEN    <span class="string">&quot;\033[30;42m&quot;</span> <span class="comment">/* 绿底黑字 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> BLACK_YELLOW   <span class="string">&quot;\033[30;43m&quot;</span> <span class="comment">/* 黄底黑字 */</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 调试等级枚举类型定义 */</span></span><br><span class="line"><span class="class"><span class="keyword">enum</span> <span class="title">DEBUG_LEVEL</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">    DEBUG_OFF   = <span class="number">0</span>,</span><br><span class="line">    DEBUG_ERROR = <span class="number">1</span>,</span><br><span class="line">    DEBUG_WARN  = <span class="number">2</span>,</span><br><span class="line">    DEBUG_INFO  = <span class="number">3</span>,</span><br><span class="line">    DEBUG_ALL   = <span class="number">4</span></span><br><span class="line">&#125;;</span><br><span class="line"><span class="comment">//===========================================================================</span></span><br><span class="line"><span class="comment">/* 自定义类型和字体颜色 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> MYDEBUG(TYPE, COLOR, FMT, ARGS...) \</span></span><br><span class="line"><span class="meta">        do \</span></span><br><span class="line"><span class="meta">        &#123; \</span></span><br><span class="line"><span class="meta">            <span class="keyword">if</span>(DEBUG_ENABLE &amp;&amp; (DEBUG_##TYPE &lt;= LOG_LEVEL)) \</span></span><br><span class="line"><span class="meta">            &#123; \</span></span><br><span class="line"><span class="meta">                printf(COLOR); \</span></span><br><span class="line"><span class="meta">                printf(<span class="string">&quot;[%s][%s:%s:%d]&quot;</span>FMT, TYPE, __FILE__, __FUNCTION__, __LINE__, ##ARGS); \</span></span><br><span class="line"><span class="meta">                printf(CLS_AL<span class="string">L&quot;\n&quot;</span>); \</span></span><br><span class="line"><span class="meta">            &#125; \</span></span><br><span class="line"><span class="meta">        &#125; while(0)</span></span><br><span class="line"><span class="comment">//===========================================================================</span></span><br><span class="line"><span class="comment">/* 平时调试使用 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;time.h&gt;</span> <span class="comment">// 时间函数用</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> filename(x) (strrchr(x,<span class="string">&#x27;/&#x27;</span>)?(strrchr(x,<span class="string">&#x27;/&#x27;</span>)+1):x)</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> NORMAL_DEBUG 1 <span class="comment">// 注意使用下边两个宏需要自己添加换行，比较符合平时的习惯</span></span></span><br><span class="line"><span class="comment">// 获取时间函数</span></span><br><span class="line"><span class="type">char</span> *<span class="title function_">timeString</span><span class="params">(<span class="type">void</span>)</span></span><br><span class="line">&#123;</span><br><span class="line">  <span class="class"><span class="keyword">struct</span> <span class="title">timespec</span> <span class="title">ts</span>;</span></span><br><span class="line">  clock_gettime(CLOCK_REALTIME, &amp;ts);</span><br><span class="line">  <span class="class"><span class="keyword">struct</span> <span class="title">tm</span> *<span class="title">timeinfo</span> =</span> localtime(&amp;ts.tv_sec);</span><br><span class="line">  <span class="type">static</span> <span class="type">char</span> timeString[<span class="number">30</span>];</span><br><span class="line">  <span class="built_in">sprintf</span>(timeString, <span class="string">&quot;%.2d-%.2d %.2d:%.2d:%.2d&quot;</span>, </span><br><span class="line">          timeinfo-&gt;tm_mon + <span class="number">1</span>, </span><br><span class="line">          timeinfo-&gt;tm_mday, </span><br><span class="line">          timeinfo-&gt;tm_hour, </span><br><span class="line">          timeinfo-&gt;tm_min, </span><br><span class="line">          timeinfo-&gt;tm_sec);</span><br><span class="line">  <span class="keyword">return</span> timeString;</span><br><span class="line">&#125;</span><br><span class="line"><span class="comment">// 获取系统时间戳 单位 ms</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">sys_pts_get_ms</span><span class="params">(<span class="type">void</span>)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="class"><span class="keyword">struct</span> <span class="title">timespec</span> <span class="title">tv</span>;</span></span><br><span class="line">    <span class="type">long</span> <span class="type">long</span> lasttime = <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line">    clock_gettime(CLOCK_MONOTONIC, &amp;tv);</span><br><span class="line">    lasttime = tv.tv_sec * <span class="number">1000</span> + tv.tv_nsec / (<span class="number">1000</span> * <span class="number">1000</span>);</span><br><span class="line">    <span class="keyword">return</span> lasttime;</span><br><span class="line"></span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> HKPRT(fmt...) \</span></span><br><span class="line"><span class="meta">        do \</span></span><br><span class="line"><span class="meta">        &#123; \</span></span><br><span class="line"><span class="meta">            <span class="keyword">if</span>(NORMAL_DEBUG) \</span></span><br><span class="line"><span class="meta">            &#123; \</span></span><br><span class="line"><span class="meta">                printf(F_YELLOW); \</span></span><br><span class="line"><span class="meta">                printf(<span class="string">&quot;[%s][HK_LOG][%s:%d][%s]&quot;</span>, timeString(), filename(__FILE__), __LINE__, __FUNCTION__); \</span></span><br><span class="line"><span class="meta">                printf(CLS_ALL); \</span></span><br><span class="line"><span class="meta">                printf(fmt); \</span></span><br><span class="line"><span class="meta">            &#125; \</span></span><br><span class="line"><span class="meta">        &#125; while(0)</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> HKPRTE(fmt...) \</span></span><br><span class="line"><span class="meta">        do \</span></span><br><span class="line"><span class="meta">        &#123; \</span></span><br><span class="line"><span class="meta">            <span class="keyword">if</span>(NORMAL_DEBUG) \</span></span><br><span class="line"><span class="meta">            &#123; \</span></span><br><span class="line"><span class="meta">                printf(F_RED); \</span></span><br><span class="line"><span class="meta">                printf(<span class="string">&quot;[%s][HK_LOG][%s:%d][%s]&quot;</span>, timeString(), filename(__FILE__), __LINE__, __FUNCTION__); \</span></span><br><span class="line"><span class="meta">                printf(CLS_ALL); \</span></span><br><span class="line"><span class="meta">                printf(fmt); \</span></span><br><span class="line"><span class="meta">            &#125; \</span></span><br><span class="line"><span class="meta">        &#125; while(0)</span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">endif</span></span></span><br><span class="line"></span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="4-2-system-called-c"><a href="#4-2-system-called-c" class="headerlink" title="4.2 system_called.c"></a><font size=3>4.2 system_called.c</font></h3><details class="folding-tag" blue><summary> 点击查看详情 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&quot;debug_printf.h&quot;</span></span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">/* code */</span> </span><br><span class="line">    <span class="type">int</span> time0 = <span class="number">0</span>;</span><br><span class="line">    <span class="type">int</span> time1 = <span class="number">0</span>;</span><br><span class="line">    time0 = sys_pts_get_ms();</span><br><span class="line">    HKPRTE(<span class="string">&quot;This is system_called!!!\n&quot;</span>);</span><br><span class="line">    sleep(<span class="number">1</span>);</span><br><span class="line">    time1 = sys_pts_get_ms();</span><br><span class="line">    HKPRTE(<span class="string">&quot;system_called use time:%d\n&quot;</span>, time1-time0);</span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<p>这个文件我们使用以下命令编译：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">gcc system_called.c -o system_called -Wall</span><br></pre></td></tr></table></figure>

<p>然后便会生成 system_called 可执行文件，这个文件我们会在测试程序中通过system函数执行这个可执行文件。</p>
<h3 id="4-3-test-c"><a href="#4-3-test-c" class="headerlink" title="4.3 test.c"></a><font size=3>4.3 test.c</font></h3><details class="folding-tag" blue><summary> 点击查看详情 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>   <span class="comment">/* perror fgets shmat*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/shm.h&gt;</span> <span class="comment">/* shmget shmat*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/ipc.h&gt;</span> <span class="comment">/* shmget ftok */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>  <span class="comment">/* strcpy */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>  <span class="comment">/* system */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/prctl.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;fcntl.h&gt;</span>    <span class="comment">/* sem_init For O_* constants */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/stat.h&gt;</span> <span class="comment">/* sem_init For mode constants */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;semaphore.h&gt;</span><span class="comment">/* sem_init sem_post */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;pthread.h&gt;</span>  <span class="comment">/* pthread_create */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;signal.h&gt;</span> <span class="comment">/* signal */</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&quot;debug_printf.h&quot;</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">sem_t</span> sem_sys; <span class="comment">/* 定义信号量 */</span></span><br><span class="line"></span><br><span class="line"><span class="type">void</span> *<span class="title function_">thread</span><span class="params">(<span class="type">void</span> *arg)</span>;    <span class="comment">/* 读取数据线程   */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">deleteSemfile</span><span class="params">(<span class="type">int</span> sig)</span>;<span class="comment">/* 删除无名信号量 */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">sigintHandle</span><span class="params">(<span class="type">int</span> sig)</span>; <span class="comment">/* 捕获 Ctrl+\  */</span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 主函数 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line"></span><br><span class="line">	<span class="type">pthread_t</span> tid;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 信号捕获 */</span></span><br><span class="line">	signal(SIGINT, deleteSemfile);</span><br><span class="line">	signal(SIGQUIT, sigintHandle);</span><br><span class="line">	<span class="comment">/* 信号量初始化) */</span></span><br><span class="line">	sem_init(&amp;sem_sys, <span class="number">0</span>, <span class="number">0</span>);</span><br><span class="line">	<span class="comment">/* 创建线程 */</span></span><br><span class="line">	pthread_create(&amp;tid, <span class="literal">NULL</span>, thread, <span class="literal">NULL</span>);</span><br><span class="line">	<span class="comment">/* 写入数据 */</span></span><br><span class="line">	<span class="keyword">while</span>(<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		sleep(<span class="number">1</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/* 线程函数 */</span></span><br><span class="line"><span class="type">void</span> *<span class="title function_">thread</span><span class="params">(<span class="type">void</span> *arg)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">int</span> time0 = <span class="number">0</span>;</span><br><span class="line">	<span class="type">int</span> time1 = <span class="number">0</span>;</span><br><span class="line">	<span class="type">char</span> * main_name  = <span class="string">&quot;thread&quot;</span>;</span><br><span class="line">	prctl(PR_SET_NAME, (<span class="type">unsigned</span> <span class="type">long</span>)main_name);</span><br><span class="line">	pthread_detach(pthread_self());</span><br><span class="line">	<span class="keyword">while</span>(<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		sem_wait(&amp;sem_sys);</span><br><span class="line">		time0 = sys_pts_get_ms();</span><br><span class="line">		HKPRT(<span class="string">&quot;system call ./system_called\n&quot;</span>);</span><br><span class="line">		system(<span class="string">&quot;./system_called&quot;</span>);</span><br><span class="line">		time1 = sys_pts_get_ms();</span><br><span class="line">		HKPRT(<span class="string">&quot;system use time:%d\n&quot;</span>, time1-time0);</span><br><span class="line">	&#125;</span><br><span class="line">	pthread_exit(<span class="string">&quot;thread return!&quot;</span>);</span><br><span class="line">&#125;</span><br><span class="line"><span class="comment">/* 捕获 Ctrl+\ */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">sigintHandle</span><span class="params">(<span class="type">int</span> sig)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">static</span> <span class="type">int</span> count = <span class="number">0</span>;</span><br><span class="line">	HKPRT(<span class="string">&quot;I catch the SIGQUIT![%d times] \n&quot;</span>, ++count);</span><br><span class="line">	sem_post(&amp;sem_sys);</span><br><span class="line">&#125;</span><br><span class="line"><span class="comment">/* 删除信号量 */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">deleteSemfile</span><span class="params">(<span class="type">int</span> sig)</span></span><br><span class="line">&#123;</span><br><span class="line">	sem_destroy(&amp;sem_sys);</span><br><span class="line">	HKPRT(<span class="string">&quot;Destroy sem_sys!\n&quot;</span>);</span><br><span class="line">	<span class="built_in">exit</span>(<span class="number">0</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br></pre></td></tr></table></figure>
              </div>
            </details>

<p>这是我们真正的测试函数，我们使用以下命令编译：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -lpthread -Wall</span><br></pre></td></tr></table></figure>

<p>这样我们便会生成一个 a.out 可执行文件，a.out可执行文件运行后，我们在终端按下 ctrl + \ 就可以产生一个 SIGQUIT 信号。</p>
<h3 id="4-4-测试结果"><a href="#4-4-测试结果" class="headerlink" title="4.4 测试结果"></a><font size=3>4.4 测试结果</font></h3><p>我们的上边的几个文件都放在同一目录下，然后我们执行a.out 可执行文件，再按下 ctrl+\ ，会有以下内容输出：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">hk@vm:~/6temp/test$ ./a.out </span><br><span class="line">^\[01-15 15:18:19][HK_LOG][test.c:70][sigintHandle]I catch the SIGQUIT![1 times] </span><br><span class="line">[01-15 15:18:19][HK_LOG][test.c:59][thread]system call ./system_called</span><br><span class="line">[01-15 15:18:19][HK_LOG][system_called.c:10][main]This is system_called!!!</span><br><span class="line">[01-15 15:18:20][HK_LOG][system_called.c:13][main]system_called use time:1001</span><br><span class="line">[01-15 15:18:20][HK_LOG][test.c:62][thread]system use time:1004</span><br></pre></td></tr></table></figure>

<p>可以看到，我们的 a.out 中的 thread 线程执行一次一共耗时1004ms，而 system_called 可执行程序就耗费了1001ms，于是我们知道，system在某个线程中被调用的时候我们是要考虑到system执行的时间的。</p>

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